Photographic images and printing forms prepared by heat development



United States Patent 3,301,677 PHOTOGRAPHlC IMAGES AND PRINTING FORMS PREPARED BY-HEAT DEVELOPMENT Anita von Ktinig, Leverkusen, Peter Kruck, Cologne- Stammheim, and Raymund Pfeilfenschneider, Leverkusen, Germany, assignors to Agfa Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany No Drawing. Filed Sept. 22, 1964, Ser. No. 398,383 Claims priority, applicgtion 1(llse9rmany, Sept. 30, 1963,

4 Claims. (c1. 96-28) posure to an image, by the action of heat without. the

use of aqueous photographic processing baths, and the development of these layers may possibly be followed by a transfer process. In the process, those parts of the developer substances which have remained unused in the unexposed areas of the silver halide layers can be transferred to a second layer which contains one or more substances which react 'with the transferred developer substance to form non-laterally reversed positive images of the original. When using silver halide layers which contain tanning developers, the unexposed parts of the silver halide layer can be transferred to a transfer material which contains substances which blacken the silver halide of the transferred parts of the silver halide ;emulsion layer. Further, the colloid relief produced by the tanning heat development of the silver halide emulsion layer can be used as printing matrix.

The heat development and transfer processes referred to hereinbefore are described in British Patents 790,811, 801,053, and 821,506; in Belgian Patents 625,811, 637,706, 640,596, 644,162, and 644,163; and in French Patent 1,369,253.

The silver halide layers used for carrying out the above processes contain, in addition to developer substances, substances which increase the intrinsic moisture of the layer or which split off water during the heat development, such as salts containing water of crystallization, polyhydric alcohols, oligo-saccharides or caprolactam. Owing to the simultaneous presence of developer substances and substances which increase the intrinsic moisture of the layer, these layers are relatively unstable, especially silver halide layers which contain unhardened gelatin. After several months storage at room temperature or after 1-2 days storage at 40-60 C., these layers will only develop very slowly or incompletely so that in the case of tanning development, for example, the exposed areas are not sufficiently tanned by the heat development so that an imagewise transfer of portions of that layer is not possible. The main cause for this deterioration of the layers is the drying to which the layers are exposed during storage. By moistening the rear surface of the negative material, they can be restored so that they can again be developed.

Drying of the photographic layer is due to the fact that the binding agent of the layer adsorbs water and that in. photographic materials having a paper support ICC emulsion layer into the paper support. In addition, part of the emulsion layer seeps down into the paper base. The layer thus becomes so firmly anchored to its foundation that the unexposed parts can no longer be transferred or can only incompletely be transferred to the transfer material by heat. By moistening the transfer material or the negaitve, the unexposed parts of the gelatin can again be transferred.

Drying of the emulsion layer cannot be prevented by adding to the layer still more substances which increase the moisture of the layer. Layers containing too many such substances become sticky on the surface so that they become practically useless. Moreover, the photographic properties of the light-sensitive layer are impaired by the said compounds if the concentrations applied are too high.

One object of our invention is to provide a light-sensitive photographic element, which is to be processed by a heat development and transfer process and which avoids the disadvantages referred to above.

We now have found that photosensitive materials which contain an intermediate layer between the silver halide emulsion layers containing the developer and the support are excellently suitable for. heat development and transfer processes.

The said intermediate layers consist of water-soluble film-forming colloids containing hydroxy or carboxyl groups or mixtures of the said water-soluble film-forming colloids with water-dispersible polymers such as polyvinyl acetate.

Particular utility is exhibited by the following binding agents:

(1) Polyureas containing sulfo groups as described in U.S. Patent No. 2,988,538. The polyureas are prepared from diamines and diisocyanates;

(2) Alginic acids and derivatives thereof preferably alkali metal or earth alkali metal salts such as sodium alginate, potassium alkinate or calcium alginate, or esters of alginic acid in particular with alkylene glycols such as alginic acid and propylene glycol ester;

(3) Carboxyalkyl cellulose where the alkyl groups have preferably up to 3 carbon atoms, such as carboxymethyl cellulose;

(4) Carboxyalkyl starch where the alkyl groups have preferably up to 3 carbon atoms such as carboxymethyl starch; V

(5) Mixtures of derivatives of alginic acid referred to under (2) with polyvinyl acetate containing up to 30 parts by weight of polyvinyl acetate per 1 part by weight of the alginic acid derivative;

(6) Mixtures of carboxyalkyl cellulose referred to under (3) with polyvinyl acetate containing up to 30 parts by weight of polyvinyl acetate per 1 part by weight of the carboxyalkyl cellulose;

(7) Mixtures of carboxyalkyl starch referred to under (4) with polyvinyl acetate containing up to 30 parts by weight of polyvinyl acetate per 1 part by weight of carboxyalkyl starch;

(8) Mixtures of polyvinyl pyrrolidone with polyvinyl acetate containing up to 30 parts by weight of polyvinyl acetate per 1 part by weight of polyvinyl pyrrolidone.

The above film-forming agents are capable of taking up many times their own weight in water.

Simple testing will show which intermediate layer is most suitable for the particular reproduction process in which the light-sensitive element containing the intermediate layer is to be used.

some of the salts containing water of crystallization or some of the hygroscopic substances diffuse out of the In certain cases it may be advantageous toapply mixtures of the above binding agents.

The usual silver halide emulsion layers containing developer compounds as used for heat development and heat transfer processes may be applied to the intermediate layers of the present invention. Suitable silver halide emulsions and transfer materials are described in the patent specifications mentioned above.

Silver halide layers containing developer compounds are sufficiently stable when cast on the hydrophilic intermediate layers of the present invention and even after prolonged storage they develop sufliciently rapidly, so that satisfactory images, for example, relief images are obtained on the transfer material. The hydrophilic intermediate layers of the present invention may contain a smaller quantity of additional substance which provide a desired amount of moisture in the light-sensitive layer or the transfer layer during the heat development step. Such substances are compounds which split off water on heating or compounds which increase the residual moisture content of the layer. Compounds of the first mentioned type are urea, salts containing water of crystallization such as sodium citrate or preferably sodium acetate; compounds of the second mentioned type are, for example, polyhydric alcohols such as sorbitol, glycerol or polyethylene glycols. These additives are advantageous with respect to stability of the developer substances and the photographic properties of the silver halide emulsion layer such as fogging, gradation and sensitivity, and also reduce the tendency of the layers to stick.

Of particular utility for the production of positive copies is an original light-sensitive element containing an intermediate layer of a salt of polyurea sulfonic acid as the binding agent and oligo saccharides, such as sucrose, maltose and lactose.

In addition, substances which act as formaldehyde binding agents such as dimedone or semica rbazide may be added to the intermediate layers, especially when they are used with tanning heat development, the addition of these substances serving to prevent hardening of the silver halide emulsion layers due to diffusion of formaldehyde from the paper support.

The process of the present invention which is characterized by the use of photographic materials containing the intermediate layer can be advantageously used for the production of printing matrixes or stencils for screen printing. For this purpose, the exposed silver halide emulsion layer which contains a tanning developer and is applied to a suitable intermediate layer of the present invention is developed after it has been brought into contact with a suitable material for screen printing such as tissue paper or rice paper. The tissue paper can then be separated from the negative by slight moistening with water so that the developed and tanned parts of the emulsion layer adhering to the tissue paper are torn out of the emulsion layer and transferred to the tissue paper while the untanned parts of the emulsion layer remain adhering to the intermediate layer. The transferred tanned parts form on the tissue paper a relief which is impervious to dyestuffs, the screen dyes then passing through the remaining parts of the tissue paper.

EXAMPLE 1 A non-baryta-coated paper is coated with the following mixtures in the given sequence:

((1) Intermediate layer A 0.7% aqueous solution of carboxymethyl starch which contains 5 cc. of a 30% aqueous solution of saponin per liter as wetting agent, is applied to the paper and dried.

Instead of using the solution of carboxymethyl starch, the paper may be coated with the following solutions:

A 1.2% aqueous solution of carboxymethyl cellulose, or a 0.5% aqueous solution of sodium alginate, or a 0.4% aqueous solution of methylhydroxyethyl cellulose, or a 0.2% aqueous solution of galactomannan.

4 (b) Silver halide emulsion layer The following are added to a liter of a silver chloride gelatin emulsion:

0.1 g. of benztriazole (5% in alcohol),

5 g. of colloidal silicic acid,

25 cc. of a 1% aqueous solution of carboxymethyl starch, g. of sodium acetate cryst.,

5 g. of cyclohexanone bisulfite, 30 g. of pyrocatechol,

5 cc. of a 30% aqueous saponin solution.

The pH of the emulsion is adjusted to 5.3 with sulfuric acid. The emulsion is applied in known manner to the intermediate layer and dried.

Processing.The exposed negative material is developed by heating to 120 to 200 C. preferably to 160 to 185 C. for 0.5 to 30 seconds in an apparatus normally used for heat development, e.g., by means of a high gloss press, drying drum between heated rollers or. in an apparatus as described in Belgian Patent No. 628,174. A negative image which is tanned in the exposed parts is obtained. A negative image of the same quality is still obtained if the photographic material is processed after 6 to 12 months storage.

The developed negative may be brought into contact with a transfer material to producea non-laterally reversed copy, the unexposed anduntanned parts of the developed silver salide emulsion layer being transferred to the transfer material by heating to 120 to 200 C. preferably to 170 C. and are blackened there. The two papers are separated immedately after heating, a black positive image of the originalbeing obtained. on the transfer material.

Suitable transfer materials are described in Belgian Patent No. 640,596. For example, they may be produced by the following method: A non-baryta-coated paper is coated with the following solution and dried:

Onto a non-baryta-coated paper are applied the following layers in the given sequence:

(,a) Intermediate layer 15 g. of carboxymethyl starch and g. of crystallized sodium acetate are dissolved in 1 liter of water. This solution is applied to paper after the addition of 5 cc. of a 30% aqueous saponin solution and is then dried.

Instead of using the solution of carboxymethyl starch, the paper may be coated with the following solutions:

A 1.4% aqueous solution of carboxymethyl cellulose containing 150 g. of crystallized sodium acetate per liter;

A 0.7% aqueous solution of carboxymethyl starch containing 0.2 g. of a polyethylene glycol (average molecu lar weight 10,000) per liter;

A 4% aqueous solution of the sodium salt of polyurea sulfonate (prepared by polyaddition of the sodium salt of 4,4-diamino-diphenylethane-2,2-disulfonic acid with toluylene-diisocyanate) containing 20 g. of maltose, or containing 50 g. of sucrose; or

900 cm. of a 0.7% aqueous solution of alginic acid propylene glycol ester containing 130 ml. crystallized sodium acetate and 80 ml. of a 10% aqueous gelatin solution per liter, o-r

900 cm. of a 1.3% aqueous solution of sodium alginate containing 110 g. of sodium acetate and 100 ml. of a 25% aqueous dispersion of polyvinyl'acetate per liter.

' (b) SilverhaIide emulsion layer To 1 liter of a silver halide gelatin emulsion are addedz 0.5 g., of 4-hydroxy-6-methyl-1,3 ,3a,7-tetraazaindene (1% inalcohol), v p g .of colloidal silicic acid, cc. of a 1% aqueous solution of carboxymethyl starch, 110 g. of sodium acetate crysL, 3 g. of terephthalic aldehyde bisulfite, 30 g. of pyrocatechol, 5 cc. of 30% saponin. p I

The pH of the emulsion is adjusted to 5.0 with critic acid. The emulsion is applied in known manner to the intermediate layer and dried. The product is worked up as described inExar'nple .1 for which the following transfer material may be used. I r

Transfer materi'alr onto a'non-baryta-coated paper is applied the following solution and dried:

g. of carboxymethyl starch, 100 g. ofa 60% aqueous dispersion of polyvinyl acetate, 2 g. of polyethylene glycol ether (average molecular weight 10,000), r 10 g. of thiosemicarbazide, 10 g. of benzenesulfohydrazide, 1.5 g. of asynthetic ester wax, 1 l. of water.

EXAMPLE 3 This example serves to explain the production of screen printing matrixes.

Onto a non-baryta-coated paper support are applied the following layers in the given sequence:

(a) Intermediate layer 4 g. of alginic acid propylene glycol ester are dissolved in 800 cc. of water and 200 cc. of 20% polyvinyl acetate dispersion are dispersed in this solution. The paper is coated with this dispersion and dried.

(b) Silver halide emulsion layer The emulsion described in Example 1 is applied.

Processing.--The light-sensitive material is exposed to the original to be reproduced.

The exposed silver halide emulsion layer is developed in contact with rice paper as normally used for screen printing and developed in one of the apparatus mentioned in Example 1. After development, the rice paper is slightly moistened with water or the whole paper bathedfin water. The moist rice paper is now separated from the developed silver halide emulsion layer, whereby the exposed and tanned parts of the emulsion layer are torn out and transferred onto the rice paper while the unexposed and untanned portions of the developed silver halide emulsion layer remain adhered on the intermediate layer. The transferred tanned portions of the emulsion layer form a relief layer impermeable to dyes on the rice paper, so that a printing matrix or stencil for screen printing has been obtained. The said relief layer is a nonlaterally reversed negative image of the original.

Instead of the intermediate layer indicated above under (a), the following intermediate layers are also suitable for the production of printing matrixes or stencils for screen printing:

(1) 800 cc. of a 0.65% aqueous solution of alginic acid propylene glycol ester containing 45 g. of sodium acetate and 200 cc. of a 20% aqueous dispersion of polyvinyl acetate;

(2) 800 cc. of a 1.5% aqueous solution of sodium alginate containing 150 g. of sodium acetate and 200 cc. of a 40% aqueous dispersion of polyvinyl acetate;

(3) 700 cc. of a 1.3% aqueous solution of sodium alginate containing 150 g. of sodium acetate and 300 cc. of an aqueous dispersion of polyvinyl acetate (polymer content (4) cc. of a 20% aqueous solution of polyvinyl pyrrolidone, cc. of a 5% aqueous emulsion of a synthetic ester wax, and 900 cc. of a 25% aqueous dispersion of polyvinyl acetate.

EXAMPLE 4 A light-sensitive material having an intermediate layer of the present invention is used for carrying out the process described in French Patent No. 1,369,253.

The following silver halide emulsion is applied to the supported intermediate layers mentioned in Examples 1 and 2:

To 1 liter of a silver chloride gelatine emulsion are added 10 mg. of l-phenyl-5-mercaptotetrazole (1% in alcohol), 5 g. of colloidal silicic acid,

50 g. of lactose,

5 g. of cyclohexanone bisulfite,

5 g. of l-phenyl-3-pyrazolidone,

5 cc. of a 30% aqueous solution of saponin.

The emulsion is applied in known manner to the intermediate layer and dried.

A transfer material as disclosed in French Patent No. 1,369,253 is prepared as follows:

To 1 liter of a 0.5% aqueous solution of gallactomannane are added 1 g. of cobalt-leuco-phthalocyanine (marketed under the trade name Phthalogen Blue IB by Farbenfabriken Bayer AG) dissolved in 30 cc. of polyethylene glycol,

2 cc. of lactic acid,

3 g. of tartaric acid, and

5 cc. of a 30% aqueous solution of saponin.

This mixture is applied to a paper support and dried.

Processing.After exposure to the original to be reproduced, the light-sensitive material is developed at to C. for 0.5 to 30 seconds in contact with the transfer material, using the apparatus mentioned in Example 1. After separation of the two materials, a blue image is obtained on a pale yellow background. The same result is obtained if the light-sensitive material is processed after several months storage or after two days storage at 40 C. Owing to the higher moisture content, this material develops more rapidly than the previously known materials, better whites being thereby obtained on the transfer material.

EXAMPLE 5 Light-sensitive material.-As described in Example 3.

Transfer material.70 g. of the sodium salt of polyacrylic acid and 2 g. of colloidal silicic acid are dispersed in 1 liter ofwater. The casting solution is cast on a sheetlike support and dried.

Processing.--As described in Example 3.

The tanned portions of the silver halide emulsion layer are transferred onto the transfer layer of the above transfer material forming thereon a negative relief image of the original.

The process of the present invention is particularly suitable for the production of printing forms for screen printing or silk screen printing as described in Example 3. In that process portions of the light-sensitive emulsion layers are transferred to a transfer sheet which is pervious to the paste of the printing dye. Suitable are, for example, very fine mesh fabrics such as nylon or silk fabrics or some type of paper such as tissue paper or the socalled Japanese or rice paper which is silk-like and has satisfactory mechanical properties.

We claim:

1. In a supported silver halide emulsion layer containing sufficient moisture-providing ingredients to enable its development without having the layer contacted by a body of processing liquid, the improvement according to which the support under the layer is coated with an intermediate stratum of a salt of polyurea sulfonic acid,

the emulsion layer being applied over that intermediate stratum. i

2. The combination of claim 1 in which the intermediate stratum also contains moisture-providing ingredients.

3. A process for producing printing forms for screen printing, which process comprises the steps of thermally developing in contact with a screen printing sheet on'ex posed silver halide emulsion layer containing tanning developer in amount suflicient to cause the emulsion to be tanned at the exposed portions during the development, the emulsion layer being held on a support coated with an intermediate layer of a salt of polyurea sulfonic acid or 'a mixture of polyvinyl acetate and polyvinyl pyrrolidone, or salts or esters of alginic acid, or carboxyalkyl cellulose orcarboxyalkyl stanch in which the alkyl portions have up to 3 carbon atoms, moistening the screen printing sheet and separating it from the supported emulsion to cause the tanned portion of the emulsion to adhere to the sheet and come away with it while the untanned emulsion portion remains on the emulsion support.

4. A process as defined in claim 3, wherein the intermediate layer additionally contains an effective amount of a compound which contributes extra water during the development.

References Cited by the Examiner Verelst et al. 9629 NORMAN G. TORCI-IIN, Primary Examiner.

J. RAUBITSCHEK, Assistqnt Examiner. 

3. A PROCESS FOR PRODUCING PRINTING FORMS FOR SCREEN PRINTING, WHICH PROCESS COMPRISES THE STEPS OF THERMALLY DEVELOPING IN CONTACT WITH A SCREEN PRINTING SHEET ON EXPOSED SILVER HALIDE EMULSION LAYER CONTAINING TANNING DEVELOPER IN AMOUNT SUFFICIENT TO CAUSE THE EMULSION TO BE TANNED AT THE EXPOSED PORTIONS DURING THE DEVELOPMENT, THE EMULSION LAYER BEING HELD ON A SUPPORT COATED WITH AN INTERMEDIATE LAYER OF A SALT OF POLYUREA SULFONIC ACID OR A MIXTURE OF POLYVINYL ACETATE AND POLYVINYL PYHRROLIDONE, OR SALTS OR ESTERS OF ALGINIC ACID, OR CARBOXYALKYL CELLULOSE OR CARBOXYALKYL STARCH IN WHICH THE ALKYL PORTIONS HAVE UP TO 3 CARBON ATOMS, MOISTENING THE SCREEN PRINTING SHEET AND SEPARATING IT FROM THE SUPPORTED EMULSION TO CAUSE THE TANNED PORTION OF THE EMULSION TO ADHERE TO THE SHEET AND COME AWAY WITH THE UNTANNED EMULSION PORTION REMAINS ON THE EMULSION SUPPORT. 